This invention relates to apparatus for carrying out electrophoresis and related techniques such as isoelectric focusing. Since various features of the invention are applicable to electrophoretic techniques generally, the term "electrophoresis" will be taken to include these related techniques. Electrophoresis is a technique for analyzing biological fluids by separating out the proteins contained therein. A sample of the fluid to be analyzed is typically embedded in a medium, across which an electric field is applied. This causes molecules of the sample to migrate through the medium, thereby providing information for analysis.
It is common to carry out electrophoresis in a horizontal mode with the medium in an open faced format. The medium, which may be in the form of a thin coating on a slide, or a beaded aggregate in a trough, is supported on a cooling bed through which coolant fluid, typically cold water, circulates. The cooling bed is flanked by a pair of parallel electrode troughs filled with buffered saline water. A platinum electrode wire in each trough extends the length thereof. One end of each wire is connected to a respective terminal of a DC power supply, and the electrical connection to the medium is effected by wicks extending into the troughs. The components are normally enclosed within a housing, the housing typically being provided with a transparent top to allow viewing by the operator.
In the past, problems have been encountered during the actual performance of electrophoresis with apparatus as described above. During high power applications in which a high electric potential is applied to the medium, considerable heat is generated. Water evaporates, primarily from the medium and from the wicks and condenses on the inside of the cover, thereby obstructing the operator's view. A further problem with such condensation is that as it accumulates, it tends to drip from the cover back into the sample, thereby destroying the accuracy of the procedure.
Low power applications in which a relatively low electric potential is applied to the medium avoid the heat problems, but normally require a relatively long time. This may cool the medium below the dew point of the air in the housing, causing condensation on the medium. Again, this compromises the accuracy of the procedure.
A further difficulty with electrophoresis apparatus of the type described above is that the electric potential applied to the medium may vary from one end to the other. In particular, the potential across the portion of the medium nearest the ends of the wires to which the terminals of the voltage supply are connected is higher than the potential across the portion near the free end of the wires. This difference results from the small but non-negligible resistance of the wires themselves.
Thus, there is a need for electrophoresis apparatus that avoids these and other problems of prior art devices and which generally enhances the accuracy of electrophoresis, speeds up the actual tests and which is further reasonable in its cost.